Advice needed

Today, i went to the doctor because for the past 3 months usually around my period ive been feeling dizzy & nauseas. I just got off my period. My blood pressure has been low for about 3 months. They Thought it was possibility of being pregant so just incase took a test was negative. They also think its something to do with my birth control pills and the regulation and stuff. Do you think i should try a different birth control or any opinions?